1. Field of the Invention
This invention relates to a primary backing (hereinafter abbreviated to backing) for tufted carpets having improved tufting properties and tufted carpets produced from the same. More particularly, it relates to a backing for tufted carpets, comprising a polypropylene woven or non-woven fabric and having improved tufting properties, and tufted carpets produced from the same.
2. Description of the Prior Art
In the production of tufted carpets, heretofore, as a carpet backing, jute cloth (which have scarcely been currently used) and recently, woven fabrics of polypropylene tape yarns, woven fabrics of polypropylene split yarns, products obtained by needle-punching these woven fabrics with synthetic fibers or the like, non-woven fabrics of synthetic fibers produced according to spun bond process have been used. Pile yarns are pierced through these backings by using a tufting machine to prepare the so-called pile fabrics which are then fixed by back-laminating to produce tufted carpets. The process of preparing pile fabrics includes a case where loop form is left behind, as it is, in the pile and a case where the tip end of loops are cut open, to provide different kinds of tufted carpets which have been referred as loop type and cut type, respectively (see FIG. 1 and FIG. 2). Tufted carpets, whether they are of the loop type or the cut type, have an adhesive spread on the back surface of their backing for fixing piles to the backing, since the piles, as they are, slip out of the fabrics. Further, in order to hide the back surface of the tufting and make the pile fabric thick to thereby enhance the value of carpet, back laminating is carried out. Materials for this back laminating are called "secondary backing" and distinguished from the above primary backing. As the secondary backing, jute cloth, various kinds of synthetic fiber cloths, etc. are used. Further, foamed rubber, urethane resin or the like may serve at the same time for adhesion of pile for fixing and as a back-laminating backing.
In the tufting process, the pitch at which piles are planted in the backing is determined by tufting machines. The pitch between needles, as measured in the lateral direction of carpet (with direction of machine), is called "gauge" and tufting machines include those of gauges of 5/32 inch, 1/8 inch, 1/10 inch, 5/64 inch, 5/16 inch, 3/16 inch, etc. This gauge determines the pitch of piles in the lateral direction. The density of piles in the longitudinal direction of carpet (the tufting direction of machine) is called "stitch" which indicates the number of needles per 1 inch pierced through the fabric to prepare piles.
For the backing of tufted carpets, the following specific features are generally required:
(1) low penetration resistance to tufting needles; PA1 (2) uniform distribution of values of penetration resistance on the backing; PA1 (3) No slipping of piles out of the backing till back-laminating is complete after tufting, that is, retention of the so-called adequate pile-holding force; and PA1 (4) retention of a stiffness to such an extent that no crease occurs at the time of rolling up or unrolling the backing in the process of tufting and no deformation even when a certain stress or heat is applied to the backing. PA1 a primary backing for tufted carpets, produced by weaving polypropylene tape yarns oriented by stretching or tufted carpets produced from the same, the tape yarns comprising foamed polypropylene tape yarns having a foam content of 0.8 to 20%.
In the preparation of piles, tufting needles must penetrate through the backing; at that time, the less the penetration resistance and the more uniform the distribution of the values of penetration resistance, the more constant the height of piles and the more orderly their arrangement, thus affording a good pile fabric. Further, it is naturally necessary for the backing to have a pile-holding force to such an extent that the piles driven in the backing are sufficiently retained. The backing is unrolled or rolled up at the time of tufting. Further it is similarly unrolled or rolled up in the processes of application of adhesives and back-laminating, followed by applying heat for drying. Accordingly, stiffness and heat stability which are sufficient to these processes, are required.
In general, non-woven fabrics have fine fibers piled up at a uniform density in irregular directions; a low penetration-resistance to tufting needles; and a uniform distribution (needles do not penetrate through fine fibers but the clearances between fibers) (see FIGS. 3 and 4). On the other hand, the backing of polypropylene woven fabrics have more coarse constituting fibers than those of non-woven fabrics. Thus there occur cases where needles penetrate through the constituting fibers and a case where needles do not penetrate through the fibers, and a difference in the penetration resistance occurs between both the cases (see FIGS. 5 and 6). On the other hand, non-woven fabrics are weak in the pile-holding force and also weak in the stiffness of cloth due to the weakness of the constituting fibers. Whereas the backing of woven fabrics are strong both in the holding force and the stiffness of cloth, thus, it can be said that non-woven fabrics are superior in the above specific features (1) and (2), while the backing of woven fabrics are superior in the specific features (3) and (4).
In recent years, along with the trend of tufted carpets toward fine gauge (use of a tufting machine having narrow pitches between needles and increase in the number of stitches), the size of pile yarns as well as the denier of single fibers constituting the pile yarns has been reduced. In this case, the above specific features (1) and (2) are more required for the backing.
As described above, the backing of polypropylene woven fabrics have slight drawbacks in the specific features (1) and (2). As measures for the process for overcoming the drawbacks, in order to reduce the penetration resistance, (i) finishing the backing with oiling agents or (ii) reducing the denier of woven fabric-constituting fibers (raising the split quantity in the case of split yarns) has been employed, and in order to make uniform the distribution of the values of penetration resistance, (iii) making the density of woven texture higher, have been employed alone or in combination.
While these processes are respectively effective, they have of themselves limitations in respect of economy and in respect of other specific features of the backing.
Namely, according to the above process (i), with the increase in the amount of oiling agent adhered, the cost increases and depending on the kind of oiling agents, it is necessary to take into account the effect of oiling agents upon dye liquors when pile fabrics are dyed. According to the process (ii), since the denier is reduced, there is a possibility that the backing is reduced in the stiffness and strength and that it is broken; hence the reduction in the denier has a limitation. According to the process (iii), since the woven texture of the backing is caused to correspond to the pile density, the higher the pile density, the smaller the denier of tape yarns; thus the woven texture cannot help being dense, which increases the cost of the tape yarns and the weaving cost which, in turn, increase the cost of the backing. Further, even if the denier of tape yarns is reduced, the texture becomes dense; hence a problem is raised that the penetration resistance increases.
The present inventors have made extensive research on above-mentioned various problems as to the backing of polypropylene tape yarn woven fabrics and have found that when foamed tape yarns i.e. foam-containing tape yarns are used as the stock for the backing, it is possible to economically produce a backing of woven fabrics having the above specific features (1) and (2) close to those of non-woven fabrics, as well as provided with the intrinsic specific features (3) and (4).